1. Technical Field
The present invention relates to a semiconductor device and a method of manufacturing a semiconductor device.
2. Related Art
General semiconductor device is configured to have semiconductor elements such as transistors formed on a semiconductor substrate, and to have a plurality of interconnect layer formed over the transistors. In the semiconductor device thus configured, a layout of the semiconductor elements formed on the semiconductor substrate is determined based on functions required for the semiconductor device.
In recent years, investigations have been made on forming thin-film transistors using compound semiconductor layers, as described in the literatures (1) to (6):
(1) “Control of p- and n-type conductivity in sputter deposition of undoped ZnO”, Gang Xiong, et al., App. Phys. Lett., Vol. 80, No. 7, 18 Feb. 2002;
(2) “High mobility bottom gate InGaZnO thin film transistors with SiOx etch stopper”, Minlyu Kim, et al., App. Phys. Lett., Vol. 90, 212114(2007);
(3) “High mobility thin-film transistors with InGaZnO channel fabricated by room temperature rf-magnetron sputtering”, Hisato Yabuta, et al., App. Phys. Lett., Vol. 89, 112123(2006);
(4) “Highly Stable Ga2O3—In2O3—ZnO TFT for Active-Matrix Organic Light-Emitting Diode Display Application”, Chang Jung Kim, et al., IEEE Electron Devices Meeting, IEDM '06, Technical Digest, session 11.6, 2006;
(5) “Integrated circuits based on amorphous indium-gallium-zinc-oxide-channel thin-film transistors”, M. Ofuji, et al., ECS Transactions, 3(8), 293-300(2006); and
(6) “Wide-bandgap high-mobility ZnO thin-film transistors produced at room temperature”, Elvira M. C. Fortunato, et al., App. Phys. Lett., Vol. 85, No. 13, 27 Sep., 2004.
If the functions of the semiconductor device may be modified while leaving the layout of the semiconductor elements formed on the semiconductor substrate unchanged, now a plurality of types of semiconductor devices having different functions may be manufactured using the same semiconductor substrate. In this case, costs for manufacturing the semiconductor device may be saved. On the other hand, the interconnect layers over the semiconductor substrate have included only interconnects, capacitor elements, fuses and so forth, so that functions of the semiconductor device have been changeable only to a limited degree, simply by modifying configuration of the interconnect layer. It is, therefore, expected to largely modify the functions of the semiconductor devices without changing the layout of the semiconductor elements formed on the semiconductor substrate, if any element having new function may be formed in the interconnect layer.